\begin{table}[!ht]
\centering
\caption{}
\label{}
\begin{threeparttable} \noindent\makebox[\textwidth]{ 
\begin{tabular}{lccccc}
\toprule
 & \multicolumn{2}{c}{Overall} & Cover & No Cover & $p$-value \\
 \cmidrule(r){2-3} \cmidrule(lr){4-4} \cmidrule(lr){5-5} \cmidrule(lr){6-6} 
 & mean & std.~dev. & mean & mean & (C = NC) \\
%\cmidrule(r){2-2} \cmidrule(lr){3-3} \cmidrule(lr){4-4} \cmidrule(lr){5-5} \cmidrule(l){6-6} 
 \midrule 
\bottomrule
\end{tabular}}
\begin{tablenotes}[flushleft] \footnotesize
\item \textit{Notes: }$p$-values based on robust standard errors reported. Ideology is coded from -2 (very liberal) to 2 (very conservative).
\end{tablenotes} 
\end{threeparttable} 
\end{table}
